This invention relates to telecommunications systems for the hearing impaired, and more specifically to a system and method for enabling communications through a public telecommunications network between a party using a TDD device and a party not so equipped.
There are various networks, public and private, that may be used for telephone communication. The public system we are all familiar with is often referred to as the public switched telephone network (PSTN). FIG. 1 (prior art) is a simplified block diagram illustrating the basic configuration of an exemplary PSTN 100. In general terms, PSTN 100 typically comprises numerous local exchanges, which may also be referred to as central offices (COs). Each CO is connected to dozens or even hundreds of telephone service subscribers, although for simplicity only two are shown in FIG. 1, designated as party 1 and party 2. (The terms xe2x80x9cuserxe2x80x9d and xe2x80x9csubscriberxe2x80x9d will be used interchangeably herein.) COs may be connected to each other either directly or though other telephone offices in order to properly route telephone calls. Two or more COs may be connected by a tandem office (TO), which may be viewed as the next higher level in a hierarchical network structure. A primary toll center may connect the various COs and tandems of a particular telephone company and themselves be connected to primary toll centers operated by others (not shown). The primary toll centers (PTC) of a given region may be connected to a sectional toll center (STC), a number of which may be connected with a regional toll center (not shown). Note that the illustrated PSTN 100 hierarchy is exemplary and is not employed in all systems. Where it exists, however, calls are usually routed through the lowest common switching level, with higher level offices used only for calls that are to terminate outside of the network below them. Party 1 and party 2 are typically but not necessarily located at a home or business site. In this illustration, party 1 may be the calling party and party 2 the called party. The call between them may be connected from their respective COs through a tandem office. Note the majority of telephone calls are two-party calls. The calling party initiates the process by opening up a dedicated circuit that will be used until the call is completed. This is true even where one or both of the parties are not human, such as when one fax machine xe2x80x98callsxe2x80x99 another. In some cases, more than two parties may be present on a call, and such a call may be in that event initiated by a phone-company operator. Note that the system and method of the present invention is equally applicable to these multiple-party telephone calls as well, but such applications will not be discussed separately herein.
Party 1 initiates the call by xe2x80x98going off hookxe2x80x99, which in many cases is accomplished simply by raising the handset from it""s hook, but may also be accomplished in other way such as depressing a calling button on the telephone, annunciating a voice command, or similar steps. Going off hook completes a circuit between party 1""s telephone set and the CO, which is then ready to receive instructions on how to set up the remainder of the call circuit.
These instructions are given by the caller xe2x80x98dialingxe2x80x99 the telephone number of the called party. On a rotary telephone, this is actually accomplished by turning a spring-loaded dial and letting it return to its original position. Other phones are capable of instead producing a distinctive tone, or more specifically a pair of tones corresponding to each of its numbered keys. The pair of tones is sometimes referred to as a dual tone multi-frequency (DTMF) signal, and is recognizable by the PSTN. A caller using one of these touch-tone phones simply depresses the keys corresponding to a telephone number in order to place a call.
When the CO receives dialing instructions, it proceeds to set up the call. It determines the location of the called party in terms of the path that a connection to them must take. If party 2 is connected to the same local office as party 1, the connection may simply be established through the local office and goes no higher in the network hierarchy. If not, the next highest level of the network is used, and then the next highest, and so on, on until the call can be placed. The connection is maintained until the parties go on hook when the call is completed. The various network lines used for the call are then freed for other uses.
Very useful for voice communication, as it is used by most of the population, PSTN 100 is obviously of little use for those who are without the ability to hear or speak or, as is sometimes the case, without either ability. For them the wonders of instant conversation go unrealized without some additional facility. Although modern telephone networks are now capable of transmitting data as well as voice, practical limitations often still prevent conversation-like communications. For example, telephones are ubiquitous while fax machines and computers are not as readily available. To send a fax message, the intended recipient must also have a fax machine, and of course one that is turned on and already connected to a phone line. While it is not uncommon for businesses to have such situation, the fax machine frequently remains unattended, with fax messages picked up only on an occasional basis. Even where an attendant continually monitors the machine, the intended recipient is likely someone else and must await delivery. And a fax message cannot be returned until it is received by the intended recipient. Fax machines in residences are often even less helpfully situated, many of them remaining unconnected until a through a voice conversation the sender and the recipient coordinate having it hooked up to a free line so that the fax message can be sent at an agreed upon time. For these reasons, fax machines are usually not a suitable substitute for a voice conversation.
Personal computers, while increasingly common in both home and office, have similar limitations in providing conversation-quality communications. Sending electronic mail (email) messages is a form of communicating with many advantages, but actual conversation is only achieved under certain circumstances. Note that as used herein, the terms xe2x80x98conversationxe2x80x99 and xe2x80x98conversation qualityxe2x80x99 connote the ability for two (or more) parties to engage in a series of communications in a single communication session in which all parties participate substantially simultaneously. In the context of voice communication this is naturally possible, though it can also be achieved (albeit with some awkwardness) by repeated faxes or emails sent back and forth between parties in attendance at the proper devices at the same time. Computers connected to a communication network also offer the ability to xe2x80x98chatxe2x80x99, where two or more parties type in text messages that are with no significant delay displayed on the monitors of intended recipients. Again, however, absent a coincidence of users availing themselves of the same facility at the same time, chat sessions must be by advance arrangement.
Fortunately, however, a device has been developed to permit conversation between persons who are hearing (or speech) impaired. Often referred to as a telephone device for the deaf (TDD), it may be connected to a standard phone line. A TDD is a basically a telephone instrument that sends and receives text instead of voice communications. (TDDs are sometimes referred to as TTYs after the xe2x80x98teletypewritersxe2x80x99 on which they were originally modeled.) An exemplary TDD is illustrated in FIG. 2 (prior art). There, TDD 200 features a keyboard 210 used by callers to enter text for transmission. A visual display 220 may be used to read the text that is being entered and, of course to read responsive text messages as they are received. The displayxe2x80x94may be larger than that illustrated in FIG. 2, but its size is limited by the desired level of portability for the instrument. Acoustic cups 230 and 235 may be provided to receive the microphone and speaker on the handset of a standard telephone (not shown). Other TDDs may simply use a jack-type connection, such as a TDD that is designed for use with a cell phone (also not shown).
Text that is entered into the TDD via keyboard 210 is converted into tones (or, where applicable, representative electrical signals), often according to a standard known as Baudot, a universally recognized encoding scheme. The tones are, as might be expected, transmittable over ordinary phone lines. When received by the called party, the tones are converted back to text for display on the recipient""s TDD. Depending on the key-entry speed of each user, the text messages can be in this way exchanged in relatively rapid succession to provide conversation-quality communication, even for those whose speech or hearing are impaired.
In normal use, TDDs can easily be used in conjunction with telephone devices that have a visible or vibrating alarm in addition to (or instead of) an audible one. This simple modification allows the call initiation process to proceed in the usual fashion as well, that is, the caller simply dials the telephone number of the called party and waits for them to answer. The call recipient, upon noticing the incoming call, simply goes off-hook and makes any necessary TDD setup connections (such as placing the handset into acoustic cups 230 and 235) so that the TDD conversation can begin. In other words, TDDs enable two (or more) properly equipped parties to place and receive calls and engage in regular (albeit textual) telephone communication without the need for a properly connected and configured fax machine or computer.
Unfortunately a limitation exists where a person needing a TDD for telephone communication calls a person who does not (need or) have one. As the non-TDD-enabled party is restricted to voice communication no conversation will ordinarily be possible. Of course, persons who expect regularly to be contacted by TDD users may arm themselves with such a device and resort to it when an encoded call is detected. This is not the norm, however, and the cost of equipping every potential TDD call recipient would be enormous. For example, TDD users may wish to call hospitals, doctor""s offices, and fire or police stations. Although a 911 service located in a major city might be expected to be equipped for TDD calls, not all emergency calls are so placed. Nor are all calls to such entities necessarily of an emergency nature, and are therefore not appropriately made to 911 or the hospital emergency room. A patient may simply wish to know if a certain medication is currently available, for example. TDD users may also wish to contact people they normally converse with, but while they are at a location not equipped for TDD communication.
One solution to the problem of a TDD user attempting communication with another party not so equipped is to provide what is often referred to as a telecommunications relay service (TRS). A TDD user wishing to call a subscriber that does not (or may not) have a TDD begins by contacting a TRS. At he TRS, human operators are provided with TDD devices and when called by a TDD user establish a conversation using the TDD facility. Then the caller lets the operator know whom they are calling, and the operator establishes a separate connection to them. The operator then communicates with the caller using their TDD and with the called party using regular voice communication. Messages given by one party are appropriately translated and provided to the other in a format that they can understand. Although a large improvement over having no message relay system at all, TRS does have its drawbacks. First, operators may be otherwise occupied when a call is places, and waiting for one to become available may result in significant delay. In an emergency, of course, this delay could have disastrous consequences. Although a protocol could be established for signaling an emergency situation and reprioritizing TDD calls to a TRS appropriately, this is a solution that is not, however, always available. And of course this remedy would presumably not be available outside of a real emergency, and as a result regular calls that nevertheless require expedience may go unmade. For instance, a TDD user may wish to get a message to a spouse regarding the cancellation of an appointment, but know that the spouse is soon leaving to go to keep it. While not a true emergency, time is still of the essence. Secondly, the operator is, after all, human and capable of translation errors. These errors may take several message exchanges to correct simply because each message must again be translated by the human operator. Finally, the TDD user or their correspondent may be uneasy discussing personal matters with a human operator even if it can be assumed they are generally discreet.
Needed is a way for those whose telephone usage is limited by the need for a TDD to be able to call and effectively communicate with any other telephone service subscribers, regardless of whether the other subscribers are themselves using a TDD. The system and method of the present invention provide just such a solution.
To overcome the above-described deficiencies in the prior art, the present invention provides a system and method for enabling unassisted communication between a TDD user and a non-TDD user through a standard telephone network. In one aspect, the invention is an automated relay system (ARS) for use in a telecommunications switching office, the system including a controller, a TDD receiver for receiving TDD communications from a calling party over a first communication line, a translator for converting the TDD communications into a standard telecommunications protocol, and a text-to-speech (TTS) engine for receiving the standard telecommunications signal from the translator and transforming it to recognizable speech for transmission to a called party over a second communication line established by the ARS. The ARS may further include a TDD signal generator for generating TDD signals for transmission to the calling party over the first communications line. The TDD signals to the calling party may represent instructions formulated by the ARS based on predetermined criteria. The invention may further include a dual-tone multi-frequency (DTMF) decoder for receiving DTMF signals from one of the parties and translating them into instructions for the ARS. A database in communication with the ARS may to used to store pre-recorded instructional messages, in either speech or TDD format, for transmission to one of the parties at the direction of the ARS controller. In another aspect, the present invention is a method of relaying communications between a calling party using a TDD and a called party having a conventional telephone. The method includes the steps of providing an ARS comprising a controller, a TDD receiver, a translator, and a TTS converter, receiving TDD format communications from the calling party, translating them into a standard telecommunications protocol, converting them into speech, and establishing a communication link for transmitting the speech message to the called party. The method may further include selecting a pre-recorded instructional message, transmitting it to at least one of the parties, receiving a DTMF response, and decoding the DTMF response into instructions for the ARS.